Two cold hearts, will they be able to love? 

They say life isn't fair, but for Seok Jaeyeon, it was as if the world just despised her. All the things she's been through, all the things she had to do, wasn't what any ordinary teenager should be doing. She turned into a killer and she knew it. Now it's time for her to clear all her sins by returning to Seoul, where everything first started. 

Seok Jaeyeon - Sixteen, high school junior. Has long black hair and a pretty face, very thin and petite. Cold, expressionless, heartless. Rarely ever smiles, and barely ever talks unless necessary. Absolutely hates skinship with anyone except for Minji.  

Yang Minji - Seventeen, high school junior. Has medium length brown hair and a baby face. Taller than Jaeyeon, but still short. Jaeyeon's best friend ever since kindergarten, the only person that Jaeyeon talks to on a daily basis. Cheerful, nice, smart, everything that a girl wants to be. Dating Lee Sungyeol, son of one of the richest families in Seoul. Everyone is jealous of her.

Exo - Organization that Jaeyeon is in. Ruthless killers, stealers, doing everything and anything illegal whenever they feel like it. 13 members including Jaeyeon (the only girl). All love and respect Jaeyeon like a little sister, except for one that loves her even more than that. Min Seung Hyun is their boss, the one that gives them missions on who to kill, what to steal, etc.

Infinite - 'Flower boys' of Maeyeong Academy. The school that Minji attends and Jaeyeon will be attending. 7 beautiful and gorgeous rich boys. However after school hours they're also known as the one of fiercest gangs in Seoul that should not be messed with.

Oh Sehun - loves Jaeyeon deeply, acts like he hates her to hide his feelings towards her. Will always look out for her no matter what.

Kim Myungsoo - exactly like Jaeyeon, cold, expressionless, barely talks to anyone and rarely ever smiles. Also has a bad past that only Infinite knows about.    

Other characters may be introduced later. 

Will Jaeyeon be able to finally forgive herself and open her heart? Or is life just too unfair.

Will Sehun ever confess that he loves Jaeyeon? And will she return his feelings? Or will she just hate him forever. 

Will Myungsoo ever open up to anyone? Will he ever find someone to love? Or does love no longer exist. 

Everything will be revealed soon enough.